I found that it helps a *lot* to heavily starch the backing fabric before layering (I use a 1:1 solution of Sta-Flo and water), and to spray baste with 505. Starch stabilizes the fabric, making it harder for it to stretch or bend or fold over on its own. Spray basting makes a continuous connection between the 3 layers (instead of, say, connecting the layers with pins 4 inches apart). These two things have prevented puckers for me.